More thoughts as more info arrives.......
One way that the Sony A9 has trouble competing as a "sports camera" and falls down, is with it's DR IQ when using the electronic shutter, the camera automatically drops into 12 bit uncompressed RAW files in this mode.
Only when shooting with the mechanical shutter can you use 14 bit RAW files, and that means shooting at "5 Fps or less"!
I used to shoot 12 bit with the Nikon D7100 to get more shots from it's paltry buffer (8 images) the difference between those and the 14 bit files (5 images) was for the most part not great, but as a matter of good sense 14 bit give a whole lot more dynamic range.
The data stream must be enormous at 20 Fps and there's a lot going in there, to read the sensor (at it's highest speed 1/32,000 sec.) and then spit it all out, whilst feeding the non black out viewfinder, a very neat trick indeed.......it's just it's not able to do it in 14 bit mode.(yet)
If it's just a question of buffer size, (240 12 Bit RAW images) an option could have been to have say, a 100 shot buffer in 14 bit, but maybe it isn't just the buffer, it could be the shear data flow and number of processing actions at high speed which forced Sony engineers to limit the whole "shabang" to their old criticized 12 bit format which they were forced to abandon.
The "silent shutter mode" was one where wedding photographers pricked up their ears, but, to use it you are again in electronic shutter mode, wedding images need the best IQ so that feature comes at a price, 12 bit RAW That to me spells Hmmm!
So if you are happy enough with 12 bit images, which for the most part have adequate IQ, especially for sports at 24 Mps, then this isn't an issue once you have found a sports lens to mount on it...........
................but "no other sports DSLR" is limited to this!
A huge technological step for mankind?? maybe......but it looks like you will have to wait for the A10 (or later) for the real deal!